1. Field of the Invention
This invention relates to a permanent magnet material or a hard magnetic material and more particularly to a rare earth alloy permanent magnet material.
2. Description of the Prior Art
Rare earth alloy permanent magnet materials fit a wide range of applications to magnetic recording materials such as magnetic tapes, magnetic recording devices, and motors and have been finding utility in various technical fields.
There is known that nitrogen is incorporated into rare earth element-transition element type matrix alloys, particularly Sm-Fe matrix alloys, to improve the magnetic properties thereof. These permanent magnet materials are produced by pulverizing a Sm-Fe matrix alloy into minute particles not exceeding several .mu.m in diameter and subjecting the minute particles to a nitriding treatment in an atmosphere of N.sub.2 gas at a temperature in the range of from 400.degree. to 650.degree. C.
The conventional rare earth alloy permanent magnetic material, however, undergoes decomposition at temperatures exceeding 650.degree. C. While a compressed piece of pulverized particles obtained by compression molding the particles in a magnetic field is sintered to produce a permanent magnet for practical use, the retention of nitrogen and the magnetic properties of magnet are appreciably degraded. It is, therefore, impossible to form a permanent magnet for practical use by the sintering method without any sacrifice of the outstanding magnetic properties produced by the nitriding treatment.